THE ANGIOSPERMAE : ROOTS 



823 



Cortex 

 Phloem 



Xylem 

 Pith 



_ Adventitious root 

 Vascular strar^d 



Root hairs 



Fig. 821. — Hedero helix. Transverse section of stem 

 showing climbing roots with root hairs. 



free-hanging shoots do not as a rule produce holdfast roots. Apparently 

 some moisture is necessary for typical holdfasts to develop, but if there is an 

 excess of moisture or if thev are grown in water they become normal roots. 

 They may be regarded therefore as normal roots impeded in development 

 by their conditions of growth. 



Fig. 822. — Zea mois (Maize). Showing the origin of 

 stilt roots from the basal nodes of the stem. 



